Bearing seals are used to prevent contaminants from entering the bearing along the shaft. Were contaminants permitted to enter this area, rapid wear of the bearing or shaft would likely result. This causes costly downtime of equipment and significant costs in material and labor in replacing worn parts. Bearing seals are especially useful where bearings are used in very dirty areas where floating particulates are present.
Devices having seals for preventing the ingestion of contaminant along a shaft are well-known in the art, such as for example shown in U.S. Pat. Nos. 3,734,580 to Piscitelli; 3,887,199 to Sundqvist; 4,350,345 to Kalan et al; 3,575,477 to Newsome; 3,273,899 to Warnery; 3,678,809 to Doutt; 4,082,296 to Stein; and 2,925,290 to Greenwald. A number of such patents use pressurized air which is injected into an enlarged portion of the bearing cvaity and forced along the shaft to the atmosphere, thus preventing contaminants from entering the bearing.
For example, U.S. Pat. No. 3,575,477 shows an air purge system in which a portion of air supplied under pressure is utilized as an air purge and lost to the atmosphere as it flows axially between a rotating shaft and bearing housing. Another portion of the air is utilized to moisten a wiper seal. U.S. Pat. No. 3,887,199 describes a seal assembly wherein pressurized air is used to moisten a wiper seal. U.S. Pat. No. 3,887,199 describes a bearing in which pressurized air is bled from the bearing to prevent the intake of contaminants. U.S. Pat. No. 3,734,580 describes a series of notched labyrinth seals for bearings. Pressurized air is forced along the shaft and through the notches, thus preventing contaminant from entering the bearing. U.S. Pat. No. 4,350,345 shows an air seal which directs air axially along the shaft through a pair of deflector rings. Most of the foregoing seal assemblies are fairly complex, expensive, and difficult to manufacture and use.
A number of other such seal assemblies for sealing the space between a shaft or stationary pipe and a stationary support structure which receives the pipe or shaft are shown, for example, in U.S. Pat. Nos. 4,556,079 to Pfeiffer; 3,881,792 to Orain; 4,114,898 to Bainard et al; and 3,971,566 to Levisohn. However, most of these patents disclose seal assemblies whose primary purpose is to prevent escape of oil from the support structure which receives the shaft or pipe.
Accordingly, there remains a need for a pressurized seal assembly for a bearing which is simple and inexpensive to manufacture and operate, yet effective in preventing contaminants from entering a bearing.